Intel 820E manual RSL Routing, Placement Guidelines for Motherboard Routing Lengths

Intel® 820E Chipset

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2.7.2.1.RSL Routing

The RSL signals enter the first RIMM on the left side, propagate through the RIMM, and exit on the right. The signal continues through the rest of the existing RIMMs until it is terminated at VTERM. All unpopulated slots must have continuity modules in place to ensure that the signals propagate to the termination.

Figure 13. RSL Routing Dimensions

	RIMM_0	RIMM_1
MCH
0"-3.50"	0.4"-0.45"	0"-3"
A	B	C
MCH to first	RIMM to	RIMM to
RIMM	RIMM	Termination	rsl_route

To maintain a nominal 28 Ω trace impedance, the RSL signals must be 18 mils wide. To control crosstalk and odd/even-mode velocity deltas, there must be a 10 mil ground isolation trace routed between adjacent RSL signals. The 10 mil ground isolation traces must be connected to ground with a via every 1 inch. A 6 mil gap is required between the RSL signals and the ground isolation trace. These signals must be length-matched to ±10 mils in line section A and to ±2 mils in line section B, using the trace length matching methods in Section 2.7.2.6. To ensure uniform trace lines, trace width variation must be uniform on all RSL signals at every neckdown for each line section. All RSL signals must have the same number of vias. It may be necessary to place vias on RSL signals where they are not necessary to meet this via loading requirement (i.e., dummy vias).

Table 3. Placement Guidelines for Motherboard Routing Lengths

Reference	Trace Description	Maximum Trace Length (in.)
A	MCH to first RIMM connector	0 to 3.50
B	RIMM to RIMM	0.4 to 0.45
C	RIMM to termination	0 to 3

Design Guide 35